The invention relates to closures for containers. The invention relates more particularly to closures that are re-closable after initial opening.
A commonly used type of closure for consumer product containers used for packaging various types of products such as vegetable shortening, coffee, powdered drink mixes, and others, includes a metal ring double-seamed onto the top end of the container. The metal ring defines a large central opening for access to the product. A flexible membrane lid is heat-sealed to the top surface of the ring to seal the product in the container. To provide reclosability, a plastic overcap fits over the outer rim of the metal ring. After the membrane lid is peeled off the ring upon initial opening of the container, the overcap can be replaced to provide some level of protection of the remaining product from the outside environment.
The overcap adds a significant cost to the package. It would be desirable to omit the overcap, but then some other way of reclosing the package would be needed. It has been proposed to provide a pressure-sensitive adhesive (PSA) on the membrane lid so that it can be re-adhered to the metal ring after initial opening. However, when powdery products are contained in the package, the powder tends to contaminate the PSA and render it less tacky than what is required for a good re-seal.